Star Lifecycle
The Lifecycle of the star has 8 stages. It starts as a Nebulae, forming into a star, then into a red giant, to a red dwarf, into a white dwarf, then there is a supernova, forming a neutron star and the last being a black hole.
Nebula
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A Nebulae is the starting point for a star, it is the birthplaces of stars. A Nebulae is simply a cloud of gas (hydrogen) and dust which is in space. There are all different types of Nebulae in space. The first is a Emission Nebulae. This Nebula glows brightly because of the gas in it which is energised by the stars which has already formed within. The second type is the Reflection Nebulae which is when the starlight reflects on the grains of dust in a nebulae. The third type of nebulae is the Dark Nebulae. This is a dense cloud made up of molecular hydrogen which partially or even completely absorbs the light from the stars behind them. An example of a Dark Nebulae is the Horsehead Nebulae in Orion. The last type are called Planetary nebulae and they are the outer layers of stars which are lost when a star changes from being a red giant to a white dwarf.
Star
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Simply, a star is a luminous glow of gases which are producing it's own heat and light by nuclear reactions (nuclear fusions). A star is born from a nebulae and consists of mostly hydrogen and helium gases. The surface temperature of a star can range from 2000°C to above 30 000°C, with the corresponding colours from a red to a blue-white. The brightest stars have a massive masses of 100 times the sun which is emitting as much light as millions of suns. The smallest mass than possible for a star is 8% of the sun which is 80 times the planet Jupiter, otherwise nuclear reactions would not take place. Stars live for less than a million before they start to expand and finally exploded as a supernovae. The faintest star possible is a red dwarf and it is less than one-thousandth the brightness of the sun. Objects with less than the critical mass of 8% the mass of the sun and only shining dimly are termed as brown dwarfs or a large planet and not a star. Towards the end of a star's life, it will swell to a red giant before it then starts loosing the outer layers as Planetary nebulae and finally shrinking to become a white dwarf, just like our sun will.
Red Giants
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Red Giants are just a large bright star with a cool surface. They are formed during the early stages of the evolution of a star like the sun, as it runs out of hydrogen fuel as it's centre. The approximate diameter of a Red Giant is between 10 and 100 times that of the sun. They are very bright as they are so large although the surface temperature is lower than the sun as it is about 2000°C - 3000°C. Very larger Red Giants are also often called Super Giants. Those stars have a diameter of up to 100 times that of the sun's and luminosities, which is a unit of radiant flux conventionally used by astronomers to measure luminosity of stars, often 1,000,000 times greater than the sun.
Red Dwarf
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A Red Dwarf is very cool, very faint and simply just a small star. It has been estimated to be approximately, one tenth the mass and diameter of our sun. A Red Dwarf burns very slowly and have an estimated lifetime of 100 billion years. The Proxima Centauri and Barnard's Star are both Red Dwarfs.
White Dwarf
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A White Dwarf is a very small, hot star and is the last stage in the life cycle of a star. The mass of a White Dwarf is very similar to the sun but only 1% of the sun's diameter making it approximately the diameter of Earth. The surface temperature of a White Dwarf is 8000°C or more. Although since White Dwarfs are smaller than the sun, the overall luminosity are 1% of the sun or less. A White Dwarf is the shrunken remains of normal stars which have used up all their supplies of nuclear energy. It consists of degenerate matter with a very high density due to gravitational effects. One spoonful of a White Dwarf has a massive mass of several tonnes. The dwarf cools and fades over several billions of years.
Supernova
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A supernova can be known as an explosive death of a star. It is often the results in a star obtaining the brightness of a massive 100 million suns for a short time. There are two general types of Supernovas, Type I and Type II. Type I only occurs in Binary star systems in which gas from on star falls onto a white dwarf which then causes it to explode. Type II only occurs in star that are ten times or more massive than the sun, which suffer runaway internal nuclear reactions at the ends of their lives, that lead to an explosion. These stars leave behind neutron stars and black holes. Supernovae's are thought to be a main source of element heavier than hydrogen and helium.
Neutron Stars
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Neutron stars are composed of mainly neutrons and are produced only when a supernova explodes. The explosion forces protons and electrons to combine to produce a neutron star. These stars are very dense and have a mass of three times the mass of the sun although only a 20km diameter. If the mass of a neutron star was any greater is would shrink further to become a black hole. Pulsars are believed to be neutron stars spinning very rapidly.
Black Holes
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Black Holes are believed to have formed from a massive star at the end of their life time. The gravitational pull into a black hole is so great that nothing can escape it or would be able to survive it, not even light. The density of matter in a Black Hole cannot be measured. A Black Hole distorts the place around them and can often suck neighbouring matter into them, including stars.
Here is a Star Chart showing you a variety of stars and the temperatures of them.